Either the casing core is bent into the brake cable path (happens when you use cable/wire cutters to cut the casing,) or there's too tight of a bend in the casing.
If it's the first, trim up the metal core of the cable housing, use a spoke or some other thin metal object to widen up the hole at the ends of the housing. Make sure the casing is nice and flat (the metal core is the most important part,) otherwise part of it will collapse once you apply braking pressure, and might re-create the problem.
I'd fix it, front brake failure usually happens under heavy braking (when you need it most.)
The thin cable doesn't take long to wear through if it's experiencing undue friction/rubbing somewhere.
Did you use ferrules on the ends of the cable housings? Cable hangers can damage housings if a ferrule isn't used.